Demirjian Four-Teeth Age Estimation in Thai Children and Adolescents: A Population-Specific Radiographic Validation Study

Background/Objectives: Dental age estimation is widely used in clinical and forensic practice. The Demirjian four-teeth methods were developed to simplify age assessment; however, their accuracy varies among populations and requires validation before use in specific ethnic groups. This study aimed to evaluate and compare the accuracy of Demirjian’s four-teeth methods I and II for dental age estimation in Southern Thai children and adolescents aged 7–15 years. Methods: This retrospective cross-sectional study included 360 digital panoramic radiographs (180 males and 180 females) from Southern Thai individuals aged 7–15 years. Dental age was estimated using Demirjian’s four-teeth method I (teeth 34, 35, 36, and 37) and method II (teeth 31, 34, 35, and 37). Estimated dental ages were compared with chronological ages using the Wilcoxon signed-rank test. Accuracy was assessed by mean error (ME), mean absolute error (MAE), and root mean square error (RMSE). Intra- and inter-observer reliability were evaluated using weighted kappa statistics. Results: Intra- and inter-observer agreement were excellent, ranging from 0.957 to 1.000 and 0.895 to 0.956, respectively. The mean chronological age was 11.53 ± 2.55 years. Both methods overestimated chronological age in males and females. ME ranged from 0.54 to 0.75 years, while MAE ranged from 0.97 to 1.01 years. Method II produced slightly lower estimation errors than method I. Significant differences between dental and chronological ages were found for both methods in both sexes (p < 0.05). Conclusions: Both methods overestimated chronological age by approximately one year in Southern Thai children and adolescents. Method II showed marginally lower errors; however, population-specific calibration may improve age estimation in Thai populations. These findings support the need for population-specific dental age estimation strategies, contributing to more personalized and accurate age estimation for Thai children in both clinical and forensic settings.